<template>
  <div>
    <p>{{ first.number }}</p>
    <el-button @click="doChange" type="primary">改变</el-button>
  </div>
</template>

<script>
export default {
  name: 'SysAdmin',
  data () {
    return {
      first: {
        number: 999
      }
    }
  },
  watch: {
    first: {
      handler (oldVal, newVal) {
        console.log(oldVal)
        console.log(newVal)
      },
      deep: true
    }
  },
  methods: {
    doChange () {
      this.first.number = this.first.number*10
    }
  }
}
</script>